FIG. 1 of the attached drawings is a partial illustration of an axial fan 1 according to the prior art, of the type defined above. This fan 1 comprises a hub 2 whose axis is indicated by A-A. A plurality of vanes 3 (only one of which is shown in FIG. 1) extends from the hub 2, the radially outermost ends of the vanes being connected to the inner surface of an outer ring 4. In the embodiment of FIG. 1, the ring 4 has a flared front portion 4a, defining a passage whose cross section tapers towards the rear portion 4b, to which the radially outermost ends of the vanes 3 are connected. The front and the rear are defined in the air flow direction, such that the front corresponds to the intake side of the fan and the rear corresponds to the exhaust side.
In the fan according to the prior art shown in FIG. 1, the rear portion 4b of the outer ring 4 is essentially cylindrical.
A fan of this type is typically made from one piece of plastic material, by injection molding.